Resting Fischer-344 rats underwent a decrease in heart rate and an increase in diastolic blood pressure and plasma norepinephrine with increasing age. The heart rate and blood pressure responses of 28-month old rats were reduced as compared to 3-month old animals, although maximal norepinephrine release was unchanged. 2. Local glucose utilization (LGU) tends to increase in sympathetic ganglia between 12 and 14 months of age in the Fischer-344 rat. The increase is statistically significant in the superior cervical ganglia, and may be related to increased circulating norepinephrine. 3. Paraganglia, which contains catecholamines and are extra-adrenal chromaffin tissue, degenerate after birth in the rat but reappear between 24 and 33-months of age, and contain high concentrations of catecholamines. 4. Catecholamine fluorescence mapped from single neuron pericarya decreased with age in certain peripheral sympathetic ganglia as well as in certain brain regions which contain catecholamine-containing neurons.